Telephone system



8 Sheets-Sheet 2 mmwu INVENTOR JOHN H voss i' ATTORNEYS J. H. VOSSTELEPHONE SYSTEM Filed April 22, 1940 RS3 @GEQ a winin Oct. 26, 1943.

Oct 26, 1943- I J. H. voss 2,333,038

TELEPHONE SYSTEM Filed April 22. 1940 a Sheets- Sheet 4 T0 LINE 45/\DIAL TONE ATTORNEYS v Oct. 26, 1943. J. H. voss TELEPHONE SY STEM FiledApril 22, 1940 8 Sheets-Sheet 5 INVENTOR JOHN H. VOSS BY M, M, W

ATT-O R N EYS Oct. 26, 1943. J. H. voss TELEPHONE SYSTEM Filed April 22.1940 8 Sheets-Sheet 8 INVENTOR JOHN HmVOSS ATTORNEYS atented 3943TELEPHONE SYSTEM John H. Voss, Downers Grove, 111., assignor toAntomaticElectric Laboratories, Inc., a corporation of DelawareApplication April 22, 1940, Serial No. 330,975 11 Claims. -(c1. 179-48)The present invention relates to automatic telephone systems and moreparticularly to improvements in automatic switching apparatus adaptedfor use in private automatic exchanges.

In private automatic telephone installations serving larg commercialorganizations or the like, it is frequently desirable to providefacilities whereby the executives of the organization may obtain accessto any line of the system at any time. This form of service has beencharacterized as executive right-of-way service and involves theprovision of apparatus for nabling the executive lines to obtain accessto busy called lines of the system. Prior arrangements for providingsuch facilities are exemplified by the disclosures of Stehlik Patent No.1,924,661, granted August 29, 1933, and Stehlik Patent No. 1,934,384,granted November 7, 1933. In the arrangements disclosed by thesepatents, provisions are made respond to different groups of lines of thesystem, the subgroup relays correspond to a particuon aper line basisfor marking the executive lines in a special manner in the banks of therotary finder switches of the system so that th finderconnector linkcircuits may be controlled from the executive substations to establisheddry talking circuits to busy called lines of the system.

It is an object of the present invention to provide, in an automatictelephone system of the character indicated, improved apparatus forenabling the executives served by the system to have right-of-wayfacilities, which is simple and economical in arrangement, requires a,minimum of special equipment, and is positive and reliable in operation.f

It is a further and more specific object of the invention to provideimproved apparatus of the character described, wherein the executiverightof-way facilities ar primarily incorporated in the equipment whichis common to the switching links of the system.

In the illustrated embodiment of the invention there are provided aplurality of finder-connector links of theall-relay type, which, inconjunction with equipment common to the links and including a linkdistributor, operate to set up connections between the lines of thesystem. In-a'ccordance with the present invention, provisions are madewhereby right-of-way facilities are provided for the executive lines ofthe system under the control of certain of the apparatus embodied in theequipment common to the finder-connector links. More specifically, thiscommon equipment includes auxiliary group, unit and subgroup relayswhich correspond to the group, unit and subgroup relays provided in eachlar subgroup of lines in each line group, and the unit relaysrespectively correspond to the same lines in each group. These auxiliaryrelays, as incorporated in the common equipment, are arrangedselectively'to control executive rightof-way circuits which extend tothe several links, each link being provided with a right-of-way orspecial service relay which, when energized over its associatedright-of-way circuit, operates in conjunction with the busy test relayof the link to establish a talking circuit to a busy called lineselected by the connector portion of the link. With this arrangement theexecutive lines may be connected in the banks of the link-finderswitches to have the same unit directory number designations. With theseline terminated in this manner, the right-of-way circuits may beconnected to be set up by a predetermined one or more of the unit relaysoperating in conjunction with the tens or group relays respectivelycorresponding to th line groups which include the executive lines. Thesecircuits are also appropriately controlled by the link distributor andthe subgroup relay of the common equipment, so that the right-of-way orspecial service relay of an assigned link will only be operated when thefinder portion of the link operates to seize a calling executiv linearranged for right-of-way service.

Further'features of the invention pertain to the particular arrangementof the circuit elements whereby the above and d i n l p ing features areattained.

Th novel features believed to be characteristic of the invention are setforth with particularity in the appended claims. The invention, both asto its organization and method of operation, together with furtherobjects and advantages thereof, will best be understood by reference tothe specification taken in connection with the accompanying drawings, inwhich Figures 1 to 8, inclusive, when combined in the manner illustratedin Fig. 9 of-th drawings, illustrate one link and the common equipmentof an all-relay automatic telephone system having incorporated thereinthe features of the invention briefly outlined above.

Referring. to the drawings, the system there illustrated comprises 'aprivate automatic exchange at which may be terminated as many as onehundred lines, certain of which have been of the link finders. The grouprelays also corindicated in the drawings by the directory numberdesignations thereof. More specifically,

2 these lines are divided into groups of ten each, the line H extendingto the substation A being the first line of the first group, the line Iextending to the substation B being the tenth line of the first group,and the-line 0i, illustrated in Fig. 4 of the drawings, being the firstline of the tenth group. For switching purposes, each group of lines isfurther divided into two subgroups in accordance with the unitdesignations of the lines therein. Thus, the lines designated by thedirectory numbers ll, l2, l0, l4 and I5 comprise one subgroup of linesin the first group, and the lines l0, l1, l0, l0 and I0 comprising thesecond subgroup of lines in the first group.

For the purpose of setting up connections between the various lines ofthe system, there are provided a plurality of finder-connector links ofthe all-relay type. one of which is illustrated in Figs. 2, 3, 4, '7 and8 of the drawings. These links are arranged to be controlled by commonequipment which comprises a link distributor, also shown in Fig. '7 ofthe drawings, a group of distributor control relays illustrated in Fig.6 of the drawings, and a group of guard or auxiliary relays which areillustrated in Fig. 5 of the drawings. More specifically, the finderportion of the link comprises ten group relays, two of which areindicated at R200 and R2l0, which respectively correspond to thedifferent groups of lines. These relays are preferably of the characterdisclosed and claimed in Patent No. 2,135,832 granted November 11, 1938,to Herbert F. Obergfell, and only two thereof have been shown in theinterest of simplifying the disclosure. The finder portion of the linkalso comprises flv'e unit relays, each of which corresponds to two linesin each oi,the ten line groups. Thus, the relay R220, for example, isoperative in conjunction with any one of the group relays to select thelines having the unit designations of 5 and 0 in the selected group oflines. Similarly, the unit relay R200 corresponds to the lines I and 6in each of the ten different groups of lines. It will be understood thatwith one of the group relays and one of the unit relays operated, twolines are selected from the plurality of lines to which the finderswitch has access. In order to select one of the two lines thus selectedby the group and unit relays, there is provided a group relay R210 whichfunctions to switch the conductors of the link line 200 between the linklines 228 and 220. For the purpose of associating the selectedrelays ofthe finder switch with the common equipment illustrated in Figs. 5, 6and 7: there are provided a pair of connect relays R200 and R230. Y

The connector portion of the link is similar to the finder switch justdescribed, in that ten group relays, including the two relays R000 andRllfl, and each including contacts terminating ten lines of the system,are provided. These relays are also preferably of the constructiondisclosed and claimed in the above cited patent to Obergfell. Theselection of a particular line from a group of lines selected throughoperation of one of the group relays is accomplished through theoperation of a counting relay network which is illustrated in Figs. '1and 8 of the drawings as comprising ten counting relays R800, R8l0,R020, R030, R040, R850, R000, R810, R000 and R000, three pulse circuitcontrol relays R150, R160 and R110, and a slow-acting pulse controlledrelay R100. This counting chain is further utilized for the purpose ofselecting the one of the ten group relays to be operated, and the sideof a selected line over which ringsubing current is to be projected insignaling a desired called substation.

The control equipment of the link comp a line relay R3l0, a slow-actinghold relay R a right-ofway or special service relay R000, and a batteryfeed impedance element 000. This apparatus further comprises .aslow-acting ring cutoff relay R300, three ringing control relays R550,R310 and R380, a busy test relay R550, a line switching relay R300,three digit transfer relays R420, R030 and R050, and a slow-to-releasetest circuit control relay R400.

As indicated above, the equipment common to the several links comprisesa plurality of guard or auxiliary relays which individually correspondto the relays embodied in each of the finder switches. Morespecifically, this equipment comprises two group relays R500 and R5"which individually correspond to the finder group relays R2l0 and R200of the link illustrated. Eight additional auxiliary group relays areprovided, which relays are indicated by the multiple and chainconductors extending between the contacts of the two group relays R500and R5". Five auxiliary uni-t relays, including the two relays R550 andR550, are provided, which individually correspond to the five unitrelays of the various finder switches. The auxiliary relay equipmentfurther comprises a pair of relays R520 and R530 which function tocontrol the subgroup relays embodied in the finder switches.

The link distributor or ailotter equipment is also of the all-relaytype, a group of link distributor relays R100, R1l0, R100, etc., beingprovided which individually correspond to the links and operate in acyclic manner to assign the respective associated links for use in apredetermined order. These link distributor relays are arranged to becontrolled by a group of control relays which are illustrated in Fig. 6of the drawings as comprising a slow-acting relay R5l0 for controllingthe start circuits and the call metering device 5, a group ofslow-to-release link transfer and distributor control relays R020, R530,R500 and R550, a slow-acting distributor reset relay R050, and anall-links-busy relay R510 which is operated only when an all-busycondition of the respective associated links prevails. The relay R510 isarranged to control an all-busy meter 532 which functions to registerthose instances when calls fail due to an all busy condition of thelinks. The common equipment further includes a control relay R500 whichis provided for the purpose of controlling the executive right-of-waycircuits, referred to above and described with particularityhereinafter, in

aceordance with the operation of the two auxiliary sub-group relays R520and R500.

For the purpose of initiating the operation of the common equipment justdescribed, each line of the system is terminated in a line circuit whichconventionally comprises line and cut-oi! relays. Thus, the line H,which extends to the substation A, terminates at the exchange in a linecircuit I05 which includes a line relay RI" and a cut-oif relay RI l0.Similarly, the line II, which extends to the substation B, is terminatedat the exchange in a line circuit H5, which includes the line andcut-oi! relays RIM and RI", respectively.

Operation of the system Referring now more particularly to the operationof the apparatus, a call initiated at the substation A and intended forthe substation C may be considered by way of example. When the partyinitiating the call at the substation A re-' moves the receiver providedat this substation from its associated switchhook or cradle, a loopcircuit is established which includes the exchange battery and thewinding of the line relay RI00. This circuit extends from ground by wayof the contacts III, the conductor lie, the direct current bridge acrossthe conductors of the line II at the calling substation, the conductorIIb, the contacts I I2, and the winding of RI 'to battery. In operating,the relay RI 00 prepares, at its contacts IN, a circuit for energizingthe auxiliary unit relay R550 which corresponds to the line I I. At itscontacts I02, the relay RI00 completes a circuit for energizing theauxiliary group relay R500 which corresponds to the first group of tenlines. This circuit extends from ground by way of the contacts I02, thestart conductor CH5, the winding of R500, the contacts 506, C510, thecontacts 6I2, C580, the contacts 505 and -I6, the chain-connectedcontacts controlled by the other auxiliary group relays, and theresistor 522 to battery. When energized over this circuit the relay R500completes, at its X contacts 504', an obvious holding circuit foritself, and opens, at its contacts 505, a point in the common portion ofthe operating circuits for the ten auxiliary group relays. At itscontacts 505', 506, 501, 508 and 509, the relay R500, in operating,prepares the operating circuits for the five auxiliary unit relays. Inthe present case, however, only the auxiliary unit relay R550 isoperated, the circuit for energizing this relay extending from ground byway of the contacts 534, the winding of R520, CIM, the contacts IOI,CI43, the contacts 506, the winding of R550, the contacts 556, C511, thecontacts 6II, C516, the contacts 550 and 569, similar chain-connectedcontacts of the other auxiliary unit relays, and the resistor 568 tobattery. At its contacts 50I, the relay R500 prepares a circuit forenergizing the group relay of the assigned link. At its contacts 502 and503, the relay R500 prepares two of the executive right-of-way controlcircuits referred to above.

When energized in series with the relay R550 over the above-tracedcircuit, the slow-to-release relay R520, at its contacts 52I, opens a,point in the operating circuit for the relay R530, thereby to preventoperation of the latter relay until the call in progress is extended toan assigned link. The auxiliary unit relay R550 also operate when theabove-traced circuit is completed, and upon operating, completes, at itsX contacts 555, an obvious locking circuit for itself. After thiscircuit is completed, the relay R550, at its contacts 550 opens a pointin the common portion of the operating circuits for all of the auxiliaryunit relays. At its contacts 551, the relay R550 prepares a circuit forenergizing the unit relay of the assigned link which corresponds to theunit designation of the calling line. At its contacts 552 and 553, therelay R550 prepares certain of the executive right-of-way circuitsreferred to above. At its contacts 55I, the relay R550 completes acircuit for energizing the connect relays of the link previouslyselected for use by the link distributor relays. Assuming that all ofthe links are idle, all of the link distributor relays are operated sothat the link illustrated is assigned to the use of the calling line II.In such case the relay R550, upon operating, completes a circuit forenergizing the two connect relays R280 and R290 in parallel, thiscircuit extending from ground by way of the contacts 55I, the commonstart lead C513, the contacts 102, 0234, and the windings of the relaysR280 and R290 in parallel to battery. The relay R290, in operating,completes, at its contacts 291, a circuit extending by way of the commonguard lead 0682 for energizing the slow-acting relay R6I0. The relayR6I0 now operates to complete, at its.contacts H3, a circuit extendingfrom ground at the contacts 614 for energizing the call metering device6", whereby the call is registered. At its contacts 6I I, the relay R6I0opens another point in'the common portion of the operating circuits forall of the auxiliary unit relays. At its contacts 6I2, the relay R6I0opens another point in the common portion of the operating circuits forall of the auxiliary group relays. Thus, the auxiliary relays areprevented from. responding to another call until the finder switchillustrated has completed its operation to seize the calling line II.The relay R280, in operating, prepares, at the contacts controlledthereby, the operating circuits for the ten group relays embodied in thefinder switch illustrated. In the case under consideration, only therelay R2I0, which terminates the first group of ten lines, is energizedin response to operation of the relay R280, the operating circuits forthe other nine relays being held open at the restored contacts of theother auxiliary group relays. More specifically, the circuit forenergizing the relay R2I0 extends from ground by way of the contacts50I, C51I, the contacts 282, and the winding of R2I0 to battery. Thisrelay, in operating, prepares, at its contacts 2 to 2I3, inclusive,connections between the conductors of the line I I and the conductors ofthe link line 228, and, at its contacts 2 I1, prepares a holding circuitfor itself. At the remaining contacts controlled by this group relay,connections are prepared between the other nine lines terminating atthese contacts and the two link lines 220 and 229.

The relay R290, upon operating, prepares the operating circuits for thefive unit relays of the finder switch. In the case under considerationonly the operating circuit for the relay R260 is completed, this circuitextending from ground by way of the contacts 532 and 551, C584, thecontacts 290, and the winding of R260 to battery. When energized overthis circuit the relay R260 operates to prepare a locking circuit foritself at its contacts 261. At its contact 26I, 262 and 263, the relayR260 connects the conductors of the calling line II to the conductors ofthe link line 228. At its contacts 260,265 and 266, the

' relay R260 connects the conductors of the line I6 to the other linkline 229. At its contacts 293, the relay R290 prepares a circuit forenergizing the subgroup relay R210. In the present case wherein the lineII is in the first subgroup of the first group of lines, the subgrouprelay R530 of the common equipment is not operated and hence theoperating circuit for the subgroup relay R210 is held open at thecontacts 603 of the restored relay R600. Accordingly, the relay R210remains in its restored position for the duration of the call underconsideration. At its contacts 296, the relay R290 prepares alternativeoperating circuits for the five unit relays of the finder switch, thesealternative circuits being held open at the restored contacts 218 of thesubgroup relay R210. At its contacts 292, the relay R290 completes amultiple holding circuit for the link distributor relay R individual tothe link illustrated, this multiple circuit extending from ground by wayof the resistor 100, the contacts 166, C232, the contacts 292, C23I, andthe winding 01' R100 to battery. At its contacts 296, the relay R290prepares the circuit for energizing the special service or executiveright-of-way relay R300.

The relay R290, in operating, also completes a. circuit for energizingthe line relay R3I0, this circuit extending from ground by way of theupper winding of R3 I 0, the conductor 230a, the contacts 29I, theresistor 233, the conductor 230b, and the lower winding of mm tobattery. When energized over this circuit the relay R3I0 operates tocomplete, at its contacts 3I2, an obvious circuit for energizing theslow-acting hold relay R320. At its contacts 3| I the relay R3I bridgesthe windings oi the battery feed impedance element 330 across theassociated line conductors. At its contacts 3I3, the relay R3l0 opens apoint in the pulsing circuit, traced hereinafter, over which the relaysof the counting chain are con trolled.

The relay R320, in operating, completes, at its contacts 324, an obviouspath for impressing ground potential upon the release conductor C301,thereby to prepare locking circuits, traced hereinafter, for certain ofthe other control relays embodied in the link. At its contacts 325, therelay R320 prepares the pulsing circuit to the relays of the countingchain illustrated in Fig. 8 of the drawings. At its contacts 32I, therelay R320 opens one of the multiple paths included in the normallycompleted holding circuit for the link distributor relay R100, thiscircuit now being closed at the operated contacts 292 of the connectrelay R290. At its contacts 323, the relay R320 completes the preparedholding circuits for the group and unit relays R2I0 and R260,respectively. More specifically, the holding circuit for the unit relayR260 extends from ground by way of the contacts 323, the finder holdlead C235, the contacts 261 and the winding of R260 to battery Theholding circuit for the group relay R2I0 extends by way of the groundedhold lead C235, the contacts 2I1 and the winding of R2I0 to battery. Atits contacts 322, the relay R320 prepares a circuit for energizing theringing control relay R310. At the contacts 322, the relay R320 alsocompletes a path for impressing ground potential upon the privateconductor lIc of the calling line II, this path extending from ground byway of the contacts 322, C233, and the contacts 215. 263 and H3, to theconductor I I0.

When the private conductor IIc of the calling line II is grounded, thisline is marked as busy in the bank contacts of the various connectorswitches, and the cut-ofi relay RI I0 is energized over an obviouscircuit. The relay RI I0, in operating, disconnects the line conductorIla from ground and disconnects the upper winding terminal of the linerelay RI00 from the conductor IIb, Thus, the line relay RI00 isdeenergized and the calling loop circuit is cleared of the impedancerepresented by the winding of this relay.

When thus deenergized, the relay RI00 restores to open, at its contactsI 0| and I02, the established locking circuits for the operated groupand unit relays R500 and R550, respectively. At its contacts IOI, therelay RI00, in releasing, also deenergizes the slow-to-release relayR520. The

relay R500, in releasing, opens, at its contactsv 50I, the above-tracedoperating circuit for the relay R2I0. At its contacts 502 and 503, therelay R500 opens two of the prepared executive right-of-way circuits. Atits contacts 504 and 505, the relay R500 reprepares the operating cirtherelay R500 opens a further point in the abovetraced circuit forenergizing the relays R520 and R550 in series. At the remaining contactscontrolled by the relay R500, the prepared operating circuits for theother four auxiliary unit relays of the common equipment areinterrupted. The relay R520, in releasing, reprepares the operatingcircuit for the subgroup relay R530. When the auxiliary unit relay R550restores, it opens, at its contacts 551, the previously traced operatingcircuit for the unit relay R260. At its contacts 555, the relay R550opens a further point in its locking circuit. At its contacts 554 and556, the relay R550 reprepares .the operating circuits for the fiveauxiliary unit relays. At its contacts-552 and 553, the relay R550further opens the prepared executive right-of-way circuits referred toabove. At its contacts 55l, the relay R550 interrupts the above-tracedcircuit for energizing the two connect relays R230 and R290 in parallel.

The two connect relays R280 and R290 now restore. The relay R280, inreleasing, opens the prepared operating circuit for the ten group relaysof the-finder switch. The relay R290, in restoring, opens the preparedoperating circuits for the five unit relays and the subgroup relay R210of the finder switch. At its contacts 291, the relay R290 opens theabove-traced operating circuit for the relay R6 I 0, causing the latterrelay to release. At its contacts 292, the relay R290 opens theabove-traced multiple holding circuit for the link distributor relayR100. The relay R now restores, and at its contacts 102, disconnects thecommon start lead C513 from the start lead C234 extending to the linkillustrated. At its contacts 10I, the relay R100 connects the commonstart lead C513 through the contacts 1I2 of the second link distributorrelay R1I0 to the start lead individual to the second link. At itscontacts 106, the relay R100 opens a further point in its lockingcircuit as traced above. At its contacts 101, the relay R100 prepares anoperating circuit for itself. At its contacts 105, the relay R100prepares a point in the chain circuit for energizing the slow-actingreset relay R660. At its contacts 103 and 104, the relay R100 opens theprepared path for short-circuiting its own winding, and prepares a pathextending through the contacts 1 I3 for short-circuiting the winding ofthe second link distributor relay R1I0. Following the operations justdescribed, the link illustrated is identified as busy in the linkdistributor relay group, and the relays of this group are in theposition required to assign the second link to the use of the nextincoming call. Shortly following the release of the relay R100, theslowacting relay R6I0 restores to open, at its contacts M3, the circuitfor energizing the metering device 6I4. At its contacts 6 and 6l2, therelay R6I0 reprepares the operating circuits for the auxiliary unit andauxiliary group relays, whereby these relays are conditioned to respondto another call. It will be noted that the operating circuits for theseauxiliary relays are held open until all of the other relay operationsrequired incident to the handling of the call in progress are completed,thus positively eliminating the possibility of two calling linesobtaining access to the same link.

As indicated previously, the operation of the common equipment and thefinder portion of an assigned link to seize a calling line is diflerent,

depending upon the unit designation of the calling line. The precedingexplanation is predicated upon the operation of the apparatus to selecta calling line included in the first subgroup of lines of a particularline group. Briefly to consider the operation of the apparatus when acall is initiated upon a line, such, for example as the line included inthe second subgroup of a particular line group, it is pointed out thatif the line relay R120 individual to this line operates, a circuit iscompleted for energizing the subgroup relay R530 in series with theauxiliary unit relay R560 corresponding to the line 10. The previouslytraced operating circuit for the group relay R500 is also completed, atthe contacts 122, when the line relay R120 operates. More specifically,the series operating circuit for the two relays R530 and R560 extendsfrom ground by Way of the lower winding of R530, the contacts 521, C162,the contacts 121, C1, the contacts 505', the winding of R560, thecontacts 556, C511, the contacts 611, C516, the contacts 5511 and 566,and corresponding chain-connected contacts of the other three unitrelays and the resistor 568 to battery. When energized over thiscircuit, the

I relay R560 is locked up in series with the lower winding of the relayR530 over a circuit including the X contacts 565. At its contacts 564,the relay R560 opens a point in the common portion of the operatingcircuits for the five auxiliary unit relays. At its contacts 562 and563, the relay R560 prepares certain of the executive right-of-waycircuits referred to above. At its contacts 561, the relay R560 preparesa circuit for energizing the unit relay R220 01 the first link, assumingthat the first link has been selected for use by the link distributorrelays. At its contacts 561, the relay R560 completes the previouslytraced circuit for energizing the two connect relays R280 and R290 inparallel. The relay R280, in operating, completes the previously tracedoperating circuit for the group relay R210. The relay R296, inoperating, prepares the operating circint for the unit and subgrouprelays of the finder switch. The relay R290 also performs the otherfunctions described above with reference to the call initiated on theline 11. The subgroup relay R530, in operating, opens, at its contacts532, the previously traced operating circuit for the selected unit relayof the finder switch, and completes, at its contacts 533, an obviouscircuit for energizing its upper winding in parallel with its lowerwinding and in series with the winding of the auxiliary unit relay R560.At its contacts 533, the relay R530 opens a point in the previouslytraced operating circuit for the slow-acting relay R520. At its contacts531, the relay R530 completes a circuit extending by way of C581 forenergizing the relay R600. The relay R600, in operating, opens, at itscontacts 601, certain of the prepared executive right-of-way circuits,and, at its contacts 602, prepares certain others of these circuits. Atits contacts 603, the relay R600 completes the prepared operatingcircuit for the subgroup relay R210 of the assigned link, this circuitextending from ground by way of the contacts 603, C683, the contacts 263and the winding of R210 to battery. When energized over this circuit therelay R210 operates and prepares a locking circuit for itself at itscontacts 211. At its contacts 211 to 216, inclusive, the relay R210disconnects the conductors of the link line 230 from the conductors ofthe link line 228, and connects the conductors of the first-mentionedlink line to the conductors of the link line 22a in preparation for theselection of a line in the secprepared alternative operating circuit forthe relay R220, this circuit extending from' round by way of thecontacts 218 and 236, C582, the contacts 561, C583, the contacts 235,'and'the winding of R220 to battery. When energized over this circuit,the relay R220 operates and prepares a locking circuit for itself at itscontacts 221. At its contacts 224, 225 and 226, the relay R220 connects'the conductors 10a, 10b and of the calling line 10 through to theconductors 230a, 2301) and C233 of the link line 230. At its contacts221 to 223, inclusive, the relay R220 preparts a connection from theline 15 to the conductors of the link line 230, but since the subgrouprelay R210 is operated, this connection is held open at the contacts211, 213 and 215. Thus, it will be apparent that, depending upon theposition of the subgroup relay R210, either of two lines may be selectedthrough operation of any one of the five unit relays embodied in thefinder switch.

When the connect relay R290 operates, it also functions to complete theoperating circuit for the line relay R810, thereby to cause thesequential operation of this relay and the hold relay R320, in themanner pointed out above. The relay'R320, in operating, completes theprepared holding circuits for the group relay R2l0, the unit relay R220,and the subgroup relay R210, these holding circuits commonly extendingby way of the grounded hold conductor C235, and branching through thecontacts 211, 221 and 211, respectively, to the windings of therespective enumerated relays. The relay R320, in operating, alsocompletes a path extending by way of the contacts 322, C233, and thecontacts 216, 226 and 216 for impressing ground potential upon theprivate conductor 100 of the calling line 10. Thus, the calling line ismarked as busy in the contacts of the connector group relays, and thecut-off relay R130 is caused to operate to disconnect the winding of theline relay R120 from across the conductors of the line 10. When therelay R120 releases, it functions to initiate the releaseof the commonequipment. in the manner explained above, it being pointed out that theseries holding circuit for the two relays R530 and R560 is interrupted,at the contacts. 121, when the line relay R120 restores. The relay R530,in restoring, reprepares, at its contacts 532, certain of the operatingcircuits for the finder unit relays, and at its contacts 536, repreparesthe operating circuit for the slow-to-release relay R520. At itscontacts 531, the relay R530 interrupts the abovetraced operatingcircuit for the relay R600. The relay R600, in releasing, rearranges theexecutive right-of-way circuits referred to above, and, at its contacts603, opens a point in the common portion of the operating circuits forthe subgroup relays of the link finder switches.

As indicated above, each time one of the finderconnector links isassigned to the use of a calling line, the link distributor relaycorresponding thereto is deenergized and releases. Thus, when the linkillustrated is seized, the corresponding distributor relay R100 iscaused to restore to extend the control leads C513, C683 and C685 to thecontacts of the distributor relay R corresponding to the second link. Ina similar manner, when the second link is assigned to the use of acalling line, the relay R1l0 is caused to release to extend the controlcircuits to the distributor relay corresponding to the third link. Thissuccessive assignment of links continues until the last link, namelythat corresponding to the distributor relay R130, is assigned to the useof a calling line. In this regard it is pointed out that in the eventthe second link corresponding to the distributor relay R1I0 is occupiedwith a call at the time the first distributor relay R100 releases, thecontrol circuits are extended through the restored contacts of the relayR1 i to the distributor relay corresponding to the third link. Further,if this third link is also occupied with a call, the control circuitsare extended through the restored contacts of the correspondingdistributor relay to the contacts of the distributor relay correspondingto the fourth link. The arrangement of the distributor is such that therelays thereof are not immediately reoperated in response to the releaseof the respective associated links. Thus, it will be observed that withthe relay R100 in its restored position, no circuit is available forenergizing this relay regardless of the position of the hold relay R620.When, however, the last link, corresponding to the distributor relayR130, is assigned for use to cause the release of this distributorrelay, a chain circuit is completed for energizing the slow-acting resetrelay R660. Under these conditions all of the distributor relays arerestored regardless of whether or not the respective associated linksare occupied with calls. Accordingly. the circuit for energizing thereset relay R660 may be traced as extending from ground by way of thecontacts 136, the chain-connected contacts of the distributor relaysother than those illustrated, the contacts 1| 6 and 105, C685, and thewinding of R660 to battery. When energized over this circuit the relayR660 operates to prepare, at its contacts 66l, a holding circuit for theall-links busy relay R610. At its contacts 662, the relay R660 completesthe operating circuits for those of the link distributor relays whichare associated with idle links. For example, if the link illustrated hasbeen released prior to the operation of the reset relay R660, theoperating circuit for the corresponding link distributor relay R100 iscompleted, this circuit extending from ground by way of the contacts662, C681, the contacts 101, C232, the contacts 32!, C231, and thewinding of R100 to battery. Obviously, if the link illustrated is stilloccupied with a call, this circuit is held open at the contacts 321, sothat the distributor relay R100 is not energized. In a similar manner,if the second link is idle, an operating circuit for the associateddistributor relay R1l0 is completed by way of the grounded conductorC661 and the contacts 1|1. Similar operating circuits are completed forthe other distributor relays which correspond to idle links. In theevent the distributor relay R100 is energized over the circuit tracedabove, this relay operates to complete a locking circuit for itselfwhich extends from ground by way of the resistor 106, the contacts 106,C232, the contacts 32I, C23 i, and the winding of R100 to battery. Atits remaining contacts the relay R100 arranges the associated controlcircuits so that the link illustrated will be assigned to the use of thenext calling line. The other distributor relays which correspond to idlelinks ar similarly locked in their respective operated positions. Whenthe distributor relays which correspond to idle links, operate, thechain circuit for energizing the reset relay R660 is broken. The relayR660, accordingly, releases after an interval to open the preparedholding circuit for the relay R610, and to open, at its contacts 662,the respective operating circuits for the distributor relays. 4

Provisions are made in the link distributing apparatus, whereby in theevent an assigned link fails to find and seize a calling line within areasonable time interval, the assigned link is released and a secondlink is assigned to the use of the calling line. To this end the commonequipment is so arranged that each time a call is initiated upon one ofthe subscribers lines, the

normally energized slow-to-release relay R666 is deenergized. Morespecifically, the relay R666 is normally energized over a circuit whichextends from ground by way of the contacts 616, the winding of R660, thecontacts 622, C616, the contacts 666 and 666, the chain-connectedcontacts of the other unit relays, and the resistor 666 to battery. Withthe relay R660 energized over this, circuit an obvious circuit forenergizing the slowto-release relay R666 is held completed at thecontacts 6. With the relay R660 operated, the operating circuit for theoverflow meter is prepared at the contacts 66!, a multiple circuit forenergizing the relay R666 is completed at the contacts 662, and theoperating circuit for the slow-acting relay R660 is held open at thecontacts 663. When any one of the five auxiliary unit relays is causedto operate in the manner previously explained. the chain portion of theabove-traced circuit for energizing the relay R636 is opened at thecontacts 666, 666, or the corresponding contacts of one of the otherauxiliary unit relays. After an interval determined by theslow-to-release characteristic of the relay R660, this relay restores toopen the completed operating circuit for the relay R660. In the eventthe assigned finder switch successfully operates to seize the callingline in its intended manner, the line circuit associated with thecalling line operates to open the start circuits to the auxiliary groupand unit relays, in the manner previously explained, before the relayR660 is released. When these start circuits are opened, the operated oneof the auxiliary unit relays is released to recomplete the above-tracedoperating circuit for the relay R660. This relay, in reoperating,recompletes the operating circuit for the relay R660. Thus, under normaloperating conditions the relay-R660 is not released during the timeinterval required for an assigned finder switch to seize the callingline to which it has been assigned.

If, for any reason, the finder portion of an assigned link fails toseize the line to which it is assigned, thereby to cause the reoperationof the relay R630 before the relay R660 is released, then the assignedlink is released and a second new link is assigned to the use of thecalling line. Thus, if the operating circuit for the relay R660 is heldopen for a sufliciently long interval of time, this relay restores toopen, at its contacts 66!, the prepared operating circuit for theoverflow meter 632, and to open, at the contacts 662, the preparedmultiple circuit for energizing the relay R630. At its contacts 666, therelay R660 completes the prepared operating circuit for the slow-actingrelay R660, this circuit extending from ground by way of the contacts616, 626 and 663, and the winding of R660 to battery. The relay R660, inoperating, opens, at its contacts "I, the prepared path forshort-circuiting the winding of the link distributor relay correspondingto the first assigned link. At its contacts 652, the relay R650completes an obvious circuit for energizing the slow-acting relay R620.The relay R620, in operating, further prepares, at its contacts 62!, thepath for short-circuiting the winding of the distributor relaycorresponding to the first assigned link. At its contacts 624, the relayR620 opens the above-traced circuit for energizing the relay R650. Atits contacts 622, the relay R620 opens a point in the normally completedcircuit for energizing the relay R630. At its contacts 623, the relayR620 completes an alternative circuit for energizing the relay R630,this alternative circuit extending from ground by way of the contacts613, the winding of R630, the contacts 623, C510, and the resistor 522to battery. When thus energized, the relay R630 reoperates to completethe operating circuit for the relay R600. The relay R640, in turn,reoperates to reprepare the circuit for energizing the overflow meter632, to complete a multiple circuit for energizing the relay R630, andto open, at the contacts 643, a further point in the operating circuitfor the relay R650. Substantially concurrently with the reoperation ofthe relay R660, the relay R650 restores to open, at its contacts 652,the operating circuit for the slow-acting relay R620. At its contacts65!, the relay R650 completes the previously mentioned path forshortcircuiting the winding of the distributor relay corresponding tothe first assigned link.

Assuming, for example, that the link illustrated is the first assignedlink, and further, that this link has failed to find the calling line towhich it was assigned, the link distributor relay R100 isshort-circuited when the relay R650 releases in the manner justexplained. The path for shortcircuiting this distributor relay extendsfrom the negative terminal of the exchange battery through the resistor625 and by way of the contacts 62E and 65!, C684, the contacts 103,G232, the contacts 202, 023i, and the winding of R100 back to thenegative terminal of the exchange battery. It is noted that theresistance value of the'resistor 625 is relatively small as comparedwith the resistance value of the resistor 108. More specifically, theresistor 108 has a resistance value of approximately 1,000 ohms, whereasthe resistor 625 has a resistance value of only 50 ohms. It will beunderstood, therefore, that when the above-traced path is completed, therelay R100 is efiectively short-circuited and caused to release. Inreleasing, the relay R100, at its contacts 102, disconnectsthe commonstart lead C513 from the start lead C234 individual to the linkillustrated, whereby the connect relays R280 and R290 are deenergizedand restore. At its contacts the relay R100 extends the common startlead to the link start lead individual to the next available idle link.Thus, if the second link is idle, and the relay R110 is operated,'thecommon start lead C513 is connected through the contacts 10! and H2 tothe start lead individual to the second link. At its contacts 106, therelay R100, in releasing, opens a point in the common portion of its twolocking circuits, as traced previously. At its contacts. 101, the relayR100 prepares its own operating circuit. At its contacts 103, the relayR100 opens the path short-circuiting its own winding. At its contacts104, the relay R100 prepares a path for short-circuiting the winding ofthe distributor relay corresponding to the next idle link, which, in thecase assumed, is the second distributor relay R1l0. At its contacts 105,the relay R100 prepares the above-traced chain circuit for enersizingthe reset relay R660. Substantially concurrently with the release of therelay R100, the

relay R620 restores to open, at its contacts 62!, the above-traced pathfor short-circuiting the winding of the distributor relay R100, and theprepared path for short-circuiting the winding-of the distributor relaycorresponding to the second assigned link. At its contacts 624, therelay R620 reprepares the operating circuit for the relay R650. At itscontacts 622 and 623, the relay R620 opens the above-traced alternativecircuit for energizing the relay R630, and reprepares the initiallytraced operating circuit for the last-mentioned relay. It will beunderstood that since one of the auxiliary unit relays illustrated inFig. 5 of the drawings is at this time still operated, the initiallytraced operating circuit for the relay R630 is open at the contacts 554,564, or the corresponding contacts of an operated one of the otherauxiliary unit relays. Accordingly, the second timing period is startedin response to the release of the relay R620.

When the common start lead C513 is disconnected from the link start leadC234 through the release of the link distributor relay R100, in themanner just explained, the two connect relays R260 and R290 restore toopen the operating circuits for the group and unit relays of the finderswitch illustrated, and to open the completed operating circuit for theline relay R310. Thus, the line and hold relays R3I0 and R320 are causedsequentially to restore in an obvious manner. At its contacts 291, therelay R290, in releasing, disconnects the conductor' C602 from ground,thereby momentarily to deenergize the relay R6l0. Since, however, groundpotential is impressed upon this conductor through operation of theconnect relays embodied in the second assigned link substantiallyconcurrently with the release of the two relays R280 and R290, the relayR6l0 is held energized and does not restore. The application of groundpotential to the link start lead extending to the second assigned linkresults in the operation of the finder portion of this link to seize thecalling line, assuming that the second assigned link is not alsodefiective. In such case, the operated ones of the auxiliary group andunit relays, illustrated in Fig. 5 of the drawings, are caused torestore so that the operating circuit for the relay R630 is recompletedbefore the relay R640 is released. Thus, the normal operation of thedistributor equipment is resumed. If, however, the second assigned linkis also defective or, for some reason, fails to seize the calling lineto cause the operation of the line circuit associated therewith, thecycle of operation of the distributor equipment, as described above, isrepeated so that the second assigned link is released and a thirdl-inkis'assigned to the use of the calling line. More specifically, thecyclic operation of the distributor equipment continues until the finderportion of one of the assigned links is successful in its operation toseize the calling line, and thus cause the release of the operated onesof the auxiliary group and unit relays illustrated in Fig. 5 of thedrawings.

In the event all of the links embodied in the exchange are busy at thetime the relay R130, corresponding to the last link, is released tocomplete the above-traced chain circuit for energizing the relay R660,none of the distributor relays are immediately energized, although theoperating circuits for all of these relays are prepared. Accordingly,the relay R660 remains in its operated position until one of the linksis released. With the apparatus in this condition, if a call isinitiated upon one 01' the lines terminating at the exchange, theauxiliary unit relay illustrated in Fig. 5 and corresponding to thecalling line, operates to impress ground potential upon the common startlead 0613, thereby to complete the operating circuit for theall-links-busy relay R610. This circuit extends by way of the groundedlead C613, the contacts 1, 13l, and the other chain-connected contactscontrolled by the distributor relays, C686 and the winding of R6 10.tobattery. When thus energized, the relay R610 locks to ground through thecontacts 61! and 66!. At its contacts 612, the relay R610 completes acircuit extending by way. of the grounded conductor C686 and thecontacts 6 for energizing the overflow meter 632, whereby the all-busycondition of the links is registered. At its contacts 614, the relayR610 opens a point in the previously traced circuit for energizing thecall metering device 6, and a pointin the operating circuit for therelay R660. At its contacts 613, the relay A610 opens a point in themultiple operating circuit for the relay R630. Shortly following theinitiation of the call, the relays R630-and R640 are caused sequentiallyto restore in the order named and in the manner previously explained.The relay R640, in releasing, prepares the operating circuit for therelay R650, and opens, at its contacts 6, the circuit for energizing theoverflow meter 632. The relay R610 remains in its operated positionuntil the all-busy condition of the links is terminated and one of thelinks is released. Thus, if the call under consideration is abandonedbefore one of the links is released, the operated ones of the auxiliarygroup and unit relays are caused to restore in a manner clearly apparentfrom the preceding explanation so that ground potential is removed fromthe common start lead C613 and the operating circuit for the relay R630is reprepared. Thus, the operating circuit for the all-links-busy relayR610 is opened but this relay remains energized over its locking circuitas traced above. Further, the relay R630 is not caused to operate sinceits operating circuit is open at the contacts 642 and 613. Accordingly,further calls initiated prior to the release of one of the links toterminate the all-links-busy condition are prevented from causingfurther operation of the overflow meter 632. It will be own winding.After a time interval determinedv by the slow-to-release characteristicof the relay R660, this relay. restores to open, at its contacts "I, thelocking circuit for the relay R010 and to open,at its contacts 602, theprepared operating circuits for the link distributor relays. The relayR610 now releases to open, at its contacts 012, the prepared operatingcircuit for the overflow meter 632, and to reprepare, at its contacts613, the operating circuit for the relay R030.- At its contacts 614, therelay R010 completes the previously traced operating circuit for therelay R660. Due to the slow-to-release characteristic of the relay R660and the slow-to-operate characteristic of the relay R060, the operationof the finder switch illustrated, to seize the calling line and thuscause the operation of the line circuit associated therewith to releasethe operated auxiliary group and unit relays, is completed before therelay R660 can operate. According y. the relays R630 and R640 are causedsequentially to reoperate before the relay R060 operates in response tothe release of the relay R010. Thus, the two relays R620 and R660 areprevented from completing the path for short-circuiting the relay R100.In the event these two relays are operated prior to operation of therelay R640. the completion of the path for short-circuiting the windingof thedistributor relay R100 is without eifect, since, under anycircumstances, the finder switch illustrated will complete its operationto seize the calling line before the relay R100 is shortcircuited.Accordingly, the short-circuiting path will be opened at the contacts262 and 32I of the apparent from the foregoing description that with therelay R660 operated, the operating circuits for all of the linkdistributor relays are prepared. Accordingly, when one of the links isreleased, the link distributor relay corresponding thereto isimmediately energized. Thus, if all of the linksare busy and the linkillustrated is the first link to'be released, the operating circuit forthe associated distributor relay R100 is completed in response to therelease of the hold relay R320 individual to this link. The relay R100,in reoperating, opens its operating circuit and locks to ground in themanner previously explained. At its contacts 102, the relay R100connects the common start lead to the link start lead C234 so that if acall is waiting the assignment of a link, the connect relays R260 andR290 are immediately energized to cause the operation of the finderswitch illustrated in the manner explained above. At its contacts 106,the relay R100 opens the above-traced operating circuit for the relayR660. 'At its contacts 103, the relay R100 prepares the previouslytraced path for short-circuiting its relays R290 and R320, respectively,before the relay R650 is caused to restore in response to release of therelay R620. Thus, even though these two relays may operate, suchoperation is, in the case under consideration, without eflect.

Continuing now with the operation of the link to extend a connection tothe called line 0|, it is pointed out that when the hold relay R320operates to impress ground potential upon the release conductor C301, acircuit is completed for energizing the slow-to-release relay R440, thiscircuit extending by way of the grounded conductor C301, the contacts396, C330, and the winding of R440 to battery. Upon operating, the relayR440 completes a path fortransmitting the usual dial tone signal overthe calling end of the connectionto inform the calling subscriber thatthe dialing operation may be started. The path traversed by the dialtone signal current may partially be traced as extending from oneterminal of the dial tone current source, not shown, the contacts 45!,4M and 42I, C320, the contacts 36!, and the condensers 341 and 340, tothe negative side of the established loop circuit extending to thecalling substation A. After traversing the windings of the receiverprovided at this substation, the dial tone current is returned to theopposite terminal of the dial tone source over the positive side of thecalling loop circuit, the upper winding of the line relay R3 and ground.

Following the operation of the relay R440, the link circuit apparatus isconditioned to respond to the impulses makingup the first digit of thedirectory number designating the desired substation 0. In this regard itis pointed out that the link circuit apparatus is so arranged that thefirst digit is utilized to determine the side of the called line overwhich ringing current is to be projected, the second digit is utilizedto select the group of ten lines including the called line, and thethird digit is utilized to select the particuaaaaoas 9 lar called linefrom the selected group of tan lines. More specifically, .a-first digitof two impulses conditions the link circuit apparatus for thetransmission of ringing current over the negative side of the calledline. A first digit comprising three impulses, on the other hand,conditions the equipment for the transmission of ringing current overthe positive side of the called line. In the present case, since theline 0| is a single party line and the signal device provided at thecalled substation C is assumed to be bridged across the conductors ofthis line in series with a condenser, a first digit of either twoorthree impulses may be dialed at the calling substation A.

Assuming that a first digit of two impulses is dialed at the callingsubstation, the relay R3|0 is twice caused to restore and reoperate.When this relay restores at the beginning of the first impulse, theoperating circuit for the hold relay R320 is broken at the contacts 3l2.At the contacts 3l3, a circuit is completed for energizing theslow-acting relay R140 in parallel with the first counting relay R800,this circuit extending from ground by way of the contacts M3, 325 and381' to the conductor C182 where it divides, one

- branch extending through the winding of R140 to battery, and the otherbranch extending by way of the contacts 154, 164 and 114, C133, and thewinding of R800 to battery. The relay R140, upon operating, opens, atits contacts 14! and 142, two points in the operating circuit for thedigit transfer relay R430, and a point in the operating circuit for theringing control relay R350. At its contacts 143, the relay R140 opens apoint in the common portion of the operating circuits for certain of theten group relays embodied in the connector portion of the link. Due tothe slow-to-release characteristics thereof, the relays R320 and R140remain operated during each 40 series of impulses.

The relay R800, upon operating at the beginning of the first impulse,completes, at its contacts 806, a locking circuit for itself, and in sooperating circuit for the relay R800. At its contacts 113, the relayR110 further prepares the circuit for energizing the second countingrelay R820. At the beginning of the open circuit period of the secondimpulse, when the line relay mm again restores, the operating circuitfor the second counting relay R820 is completed, this circuit extendingfrom ground by way of the contacts 3l3, 325 and 391', C182, the contacts154, 184 and 113, C182, the contacts 805, and the 15 winding of R820 tobattery. When thus energized the relay R820 operates and locks to groundover a path including the contacts 826, C189, the winding of R160, thecontacts 152, 018i, the contacts 361, and the release conductor C301. At

its contacts 825, the relay R820 prepares the operating circuit for thethird counting relay R840. At its contacts MP the operating circuit forthe relay R430 is further prepared. At the remaining contacts controlledby the relay R820,

5 additional circuit control operations. are performed which are of noconsequence at the present time. At the end of the open circuit periodof the second impulse, when the line relay R310 again reoperates, thepath short-circuiting the winding of the second control relay R160 isinterrupted, permitting this relay to be energized in series with thesecond counting relay R820. The relay R160 now operates to open, at itscontacts 162, the above-traced series locking circuit for the two relaysR110 and R800, causing both of these relays to restore. At its contacts16!, the relay R160 prepares an obvious multiple point in the operatingcircuits for the relays R430 and R350. At its contacts 164, the relayR160 opens a point in the'above-traced operating circuit for the secondcounting relay R820. At its contacts 163, the relay R160 prepares acircuit for energizing the third counting relay R840.

In the case under consideration, wherein a doing completes a path forshort-circuiting th first digit of two impulses is dialed at the callingwinding of the control relay R110. This locking circuit extends by wayof the grounded release conductor C301, the contacts 361, C18l thecontacts 162, the winding of R110, C188, the consubstation, no furtheroperation of the counting chain. illustrated in Fig. 8 of the drawingsoccurs. By way of more completely describing the mode of operation ofthis chain, it is pointed tacts a", and the winding of R8 to battermout, however, that in those instances where digits It will be observedthat so long as the line relay R3|0 is restored, both winding terminalsof the relay R110 are connected to ground, and accordingiy, this relayis short-circuited. At its conother than the digit two are dialed, thecounting relays operate in sequence so that at the end of the digit thecounting relay which corresponds to the numerical value of the digitremains in tacts 805, the relayR800 prepares a circuit for its operatedPosition Thus it further impulses.

energizing the second counting relay R820. At its contacts 804, therelay R800 prepares a circuit for energizing the group relay R4l0 em-qbodied in the connector portion. of the link and terminating the firstgroup of ten lines. contacts 803, the relay R800 prepares a circuit forimpressing ground potential on the private conductor of a selectedcalled line.v At'its contacts 80| and 802, the relay R800 connects'theconducare transmitted to the line relay R3i0, the operating circuit forthe third counting relay R840 is completed at the beginning of the opencircuit period of the third impulse, this circuit extend- At its mgbyway oi the grounded conductor 0182, the contacts 154 and 163, 019i,the contacts 825, and

the winding of R840 to battery. The relay R840, upon operating, locks tothe grounded release conductor C301 over a path including the contors ofthe link line 321 to the conductors of the ts 846. C189, the winding ofR150, the conlink line 480.

At the end of the open circuit period of the first impulse, the linerelay R3l0 reoperates to recomplete the circuit for energizing the holdtacts 112, 018i, and the contacts 361. when this path is completed, therelay R150 is obviously short-circuited. At the contacts 845, the relayR840 prepares the operating circuit for the fourth relay R320 and toopen the path short-circuiting counting relay R860. At its contacts 84!,the

the winding of the control relay R110. The relay R is thus energized inseries with the first counting relay R800 and operates to open, at itscontacts 112, a point in the operating circuit relay R840 furtherprepares the circuit for energizing the relay R350. At the end of theopen circuit period of the third impulse, when the line relay R3l0 againreoperates, the path short-cirfor the relay R150. At its contacts 111,the re- 75 cuiting the winding of the relay R is opened,

permitting this control relay to be energized in i w'th the thirdcounting relay R840. The relay R155 now operates to open the serieslook: ing circuit for the two relays R180 and R820, at its contacts 152,thus causing both of these relays to restore. At its contacts 15!, therelay R150 prepares an obvious multiple path in the operating circuitsfor the relays R350 and R430. At its contacts 154, the relay R150 opensa further point in the operating circuit for the relay R840. At itscontacts 153, the relay R150 further prepares the operating circuit forthe fourth counting relay R860.

The last-mentioned circuit is completed at the beginning of the opencircuit period of the fourth impulse, and extends by way of the contacts3!3, 325 and 391', C182, the contacts 153, C180, the contacts 845, andthe winding of R860 to battery. When energized over this circuit therelay R860 locks to the grounded release conductor C301 over a pathincluding the contacts 866, C188, the winding of R110, the contacts 162,C18!, and the contacts 381. When this path is completed, the winding ofthe relay R110 is obviously shortcuited. At its contacts 865, the relayR860 prepares the operating circuit for the fifth counting relay R880.At the end of the open circuit period of the fourth impulse, when therelay R3l0 again operates, the path short-circuiting the winding of therelay R110 is interrupted, permitting this relay to be energized inseries with the counting relay R860. The relay R110 now operates toopen, at its contacts 112, the series locking circuit for the two relaysR150 and R840. At its contacts 113, the relay R110 prepares theoperating circuit for the fifth counting relay R880. It is believed thatthe manner in which the remaining counting relays respond to additionalimpulses transmitted thereto through operation of the line relay R3|0will be clearly apparent in view of the preceding explanation. Thus, itwill be noted that the relays R8 0, R830, R850, R810 and R890sequentially respond to the sixth, seventh, eighth, ninth and tenthimpulses of a digit in the order named. It will be further noted thatthe relays R880 and R850 lock to ground over the lead C189 in serieswith the control relay R160; the relays R8|0 and R810 lock to groundover the lead C189 in series with the third control relay R150; and therelays R830 and R890 lock to ground over the lead C180 in series withthe control relay R110. The three enumerated control relays operatesequentially in response to succeeding impulses successively to preparethe operating circuits to the various counting relays and successivelyto release the previously operated counting relay and its associatedcontrol relay.

Shortly following the end of the first digit of two impulses dialed atthe calling substation A, the relay R140, which is deenergized throughoperation of the line relay R3I0, restores to complete theabove-mentioned circuit for energizing the relay R430. This circuitextends by way of the grounded release conductor C301, the contacts 142and 16!, C183, the contacts 426 and 454, C184, the contacts 14!, C185,the contacts 82! C433, and the winding of R430 to battery. Uponoperating, the relay R430 locks to the grounded release conductor C301over a path including the contacts 432 and the winding of R450. Whenthis locking path is completed, the winding of the relay R450 isobviously short-circuited. At its contacts 43!, the relay R430 completesa circuit for energizing the relay R380, this circuit extend -ing by wayof the grounded release conductor C301, the contacts 43!, 452 and 424,C33!, and the winding of R380 to battery. The relay R350 now operates toopen, at its contacts 381, a point in the common portion of theabove-traced locking circuits for the three control relays R150, R andR110, and the ten counting relays illustrated in Fig. 8 of the drawings.In response to this operation the two operated relays R160 and R820 aredeenergized and restore. Aside from its function to release the tworelays R160 and R820, the operation of the busy test relay R380 iswithout-effect at this time. When the relays R820 and R restore, theimpulse counting chain and associated control equipment is fullyreleased and is prepared to respond to the impulses of the second digit.Further, these two relays, in releasing, open, at the contacts 16! and82! two points in the path short-circuiting the winding of the digittransfer relay R450. The relay R450 is thus energized in series with therelay R430 over a circuit extending by way of the grounded releaseconductor C301, the winding of R450, the contacts 432, and the windingof R430 to battery. Upon operating, the relay R450 opens, at itscontacts 45!, the above-traced circuit for transmitting dial tone signalcurrent over the calling end of the connection, thereby to terminate thedial tone signal being reproduced by the receiver provided at thecalling substation. At its contacts 452, the relay R450 opens theabove-traced operating circuit for the busy test relay R360, whereby thelatter relay is caused to restore to reprepare, at its contacts 361, theseries locking circuits for the counting relays and the associatedcontrol relays R150, R150 and R110. At its contacts 454, the relay R450opens a point in the common portion of the operating circuits for therelays R350 and R430. At its contacts 453, the relay R450 prepares apoint in the common portion of the operating circuits for the ten grouprelays embodied in the connector portion of the link. Following theoperation of the relay R450, the connector portion of the link isconditioned to respond to the impulses of the second digit of thedirectory num-- ber designating the desired line.-

As indicated above, if a first digit of three impulses is dialed, theringing circuits are rearranged for the transmission of ringing currentover the positive side of the called line. In this case it will berecalled from the preceding explanation that the relay R840 is lockedenergized in series with the control relay R150 at the end of a firstdigit of three impulses. With these two relays operated, the operatingcircuit for the ringing control relay R350 is completed in response tothe release of the slow-acting relay R140, which occurs shortlyfollowing the end of the digit. The circuit for energizing the relayR350 extends by way of the grounded release conductor C301, the contacts142 and 15!, C183, the contacts 428 and 454, C184, the contacts 84!,C180, and the winding of R350 to battery. When energized over thiscircuit the relay R350 locks to the grounded release conductor C301 overa path including the contacts 358 and the winding of the digit transferrelay R450. At its contacts 355, the relay R350 completes an alternativecircuit for energizing the busy test relay R350, this circuit extendingby way of the grounded conductor C301, the contacts 355, C333, thecontacts 452 and 424, C33!, and the winding of R380 to battery. At itscontacts 35!, 352, 353 and 354, the relay R350 rearranges the ringingcircuits for ously explained.

alternative circuit for energizing the busy test.

the transmission of ringing current over the positive side of the calledline. The busy test relay R360, in operating, opens, at its contacts881, the series locking circuit for the two relays R150 and R840,causing both of these relays to restore. Thus, the impulse countingchain and the associatedcontrol relays R150, R160 and R110 are fullyreleased. When the two relays R150 and R840 restore, two points areopened, at the contacts 15l and 84!, respectively, in the pathshort-cirrelay R360, in releasing,'reprepares the locking circuits forthe ten counting relays and their associated control relays,

The impulse counting chain illustrated in Fig. 8 of the drawings, andthe associated control relays R150, R160 and R110, respond to theimpulses of the second digit in the exact manner described. Further, theslow-acting relay R140 is energized at the beginning of the firstimpulse of the second digit, and remains operated until shortly afterthe digit is ended. In the case under consideration, wherein the calledline is the first line of the tenth group, the second digit dialed atthe calling substation A will necessarily comprise ten impulses.Accordingly, at the end of the digit, the tenth counting relay R890 isenergized in series with thecontrol relay R110. Shortly following theend of the digit, the relay R140 restores to complete the preparedoperating circuit for the group relay R400, at which are terminated thelines of the tenth group. This circuit extends by way of the groundedrelease conductor C301, the contacts 142 and 11!, C183, the contacts 426and 453, C181, the contacts 892, C896, and the winding of the-grouprelay R400 tobattery. By way of completing the explanation, it ispointed out that the portion of the circuit just traced, which extendsto the contacts 892 of the counting relay R890, is common to theoperating circuits for all of the even-numbered group relays of theconnector portion, of the link. The group relays terminating the linesforming the odd-numbered groups are arranged for energization over aslightly different circuit. Thus,

if the called line to be selected is included in the first group, forexample, such that a second digit of one impulse is dialed, the groupselect relay R410 is energized over a circuit which extends by way ofthe grounded release conductor C301, the contacts 142 and 1", C183, thecontacts 426 and 453, C181, the contacts 143,- C186, the contacts 804,046i, and the winding of R4i0 to battery. Thus, the odd-numbered groupselect relays are arranged for energization over a circuit commonlyincluding the conductor C186, and, the select relays corresponding tothe even-numbered groups of lines are arranged for energize.- tion overa circuit including the conductor C181.

When the relay R400 is energized over the circuit traced above, itoperate and locks to ground over a path including the contacts 402, thewinding of the digit transfer relay R420 and the release conductor C301.When this circuit is completed, ground potential is impressed upon bothof the winding terminals of the relay R420 in the manner previrelayR360, this circuit extending byway oi the grounded conductor C801, thecontacts 4M .and 422,-C33i, and the winding of R360 to battery. At itsremaining contacts, the relay R400 connects the conductors of theassociated ten lines tothe ten link lines corresponding to and includingthe two lines-460 and 410. Thus, the conductors of the selected tenlines are extended to the contacts controlled by the ten countingrelays; the conductor of the first line in the group being connectedover the link line 480 to the contacts 801, 802 and 803 of the firstcounting relay R800, the contacts of the second line in the group beingconnected over a similar link line to the contacts of the secondcounting relay R820, and so on.

The busy test relay R360, upon operating in response to operation of thegroup select relay R400, opens, at its contacts 361, the series lockingcircuit for the two relays R110 and R890, causing both of these relaysto restore. When these relays release, two points are opened at thecontacts Hi and 892, respectively, in the path short-circuiting thewinding of the digit transfer relay R420, permitting the latter relay tobe energized in series with the group relay R400 over a circuitextending by way of the grounded release conductor, C301, the winding ofR420, the contacts 402, and the winding of R400 to battery. The relayR420 now operates to open, at its contacts 422, the above-tracedalternative operating circuit for the busy test relay R360. At itscontacts 424, the relay R420 opens a further point in the initiallycompleted operating circuit for the busy test relay. At its contacts426, th relay R420 opens a further point in the common portion of theoperating circuits for the ten roup relays embodied in the selectorportion of the link. At its contacts 423, the relay R420 preparesalternative operating and locking circuits for the busy test relay. Atits contacts 425, the relay R420 prepares a circuit for energizing thline switching and ringing control relay R390. The busy test relay R360,upon restoring in response to the operation of the digit transfer relayR420, reprepares the locking circuits for the impulse counting relaysand their associated control relays R150, R160 and R110. Following therelease of the busy test relay R360, the connector portion of the linkis conditioned to respond to the impulses of the third digit of thedirectory number designating the calledline 0 I.

The counting relays and their associated control relays operate in theexact manner described above in response to the impulses of the thirdand final digit. The relay R140 reoperates at the beginning of thisdigit and remains operated until shortly following the end of the digit.In the present assumed case, wherein the line 0| is the first line ofthe selected tenth group of lines, the third digit will necessarilycomprise only a single impulse, so that the counting relay R800 islocked energized in series with the relay R at the conclusion of thedigit. Shortly following the end of the digit, the relay R releases tocomplete the prepared circuit for energizing the relay R390, thiscircuit extending by way of the grounded release conductor 0301, thecontacts 142 and 1", C183, the contacts 425, C332, and the winding ofR390 to battery. The relay R390 now operates further to prepare thedesired talking circuit to the selected called line and the circuit fortransmitting ringing current over the called line. At its contacts 391,the relay R390 op ns a point in the above-traced pulsing circuit overwhich impulses are transmitted to the counting relays and theslow-acting relay R140. At its contacts 399, the relay R390 opens theoperating circuit for the slow-to-release relay R440. The relay R440 nowreleases to prepare, at its contacts 442, the operating circuit for theslowto-operate ringing control relay R310. At its contacts 443, therelay R440 opens a point in one of the previously traced operatingcircuits for the busy test relay R360. At its contacts 398, the relayR390 completes an alternative circuit for maintaining the operatedcounting relay R800, and its associated control relay R110, energized.This alternative circuit extends by way 01' the groundedreleaseconductor C301, the contacts 383, CH", the contacts 162, the winding ofR110, C188, the contacts 806, and the winding of R800 to battery. At itscontacts 39|, the relay R390 prepares a circuit for transmitting busy.ton current over the calling end of the connection to energize thereceiver provided at the calling substation. At its contacts 396, therelay R390 completes a test circuit including the winding of the busytest relay R360 for determining the idle or busy condition of theselected line. In this regard it will be recalled from the precedingexplanation that when a line becomes busy. ground potential i impressedupon the private conductor thereof, for the purpose of guarding the lineagainst seizure by the various connector switches oi. the system. On theother hand, if a line is idle, the private conductor thereof is markedwith negative battery potential through the winding of the cut-ofi relayembodied in the associated line circuit.

Assuming that the selected is busy, the busy test relay R360 isenergized over the test circuit, which circuit extends from groundby wayof the contacts 405, the conductor 4600, the contacts 803, C334, thecontacts 396, C336, the contacts 443 and 423, C33I, and the winding ofR360 to battery. This circuit is completed during the interval betweenthe operation or the relay R390 and the release of the slow-to-releaserel'ay R440. It will be noted that the portion of this circuit extendingfrom the contacts 803, and including-the conductor C334 is common to theodd-numbered lines of each ten line group. On the other hand, if aneven-numbered line is selected, the idle or busy condition or the lineis tested over a slightly diii'erent circuit. More specifically, thecommon portion of the alternative circuit'individual to theeven-numbered lines extends by way of the conductor C335, thecontacts391, C336, the contacts 443 and 423, 033i, and the winding ofthe busy test relay R360 to battery. When energized over the first oithe above-traced circuits, the busy test relay operates to complete alocking circuit for itself. This locking circuit extends by way of thegrounded release conductor C301, the contacts 398, 306 and 366, C331,the contacts 423, C33|, and the winding of R360 to battery. Atitscontacts 365, the relay R360 opens a point in the operating circuit forthe ringing control relay R310. At its contacts 363 and 364, the relayR360 prepares a dry talking circuit to the selected called line. At itscontacts 362, the relay R360 completes the above-mentioned circuit fortransmitting busy tone current over the calling end 01' the connectionto energize the receiver provided at the calling substation. Thiscircuit may partially be traced as extending from one terminal of thebusy tone current source by way of the contacts 30!,

native locking circuit traced above.

aasaosa 39| and 362, and the condensers 341 and 348 to the negative sideor the established loop circuit extending to the calling substation. Thecurrent traversing this circuit is reproduced by the receiver providedat the calling substation to inform the calling subscriber that thedesired connection cannot immediately be obtained. At its contacts 361,the relay R360 opens a point in the initially completed series lockingcircuit for the two relays R110 and R800. These two relays are, however,held energized over the alter- Following the operation of the busy testrelay R380, no further operation of the apparatus occurs until theconnection is released at the calling substation. The manner in whichthe link is released when the call is abandoned is described in detailhereinafter.

In the event the selected called line 0| is idle, the busy test relayR360 is short-circuited over the previously traced test circuit and,accordingly, does not operate. Shortly following the end of the thirddigit, the relay R440 releases, in the manner previously explained, toopen the busy test circuit and to complete a circuit for energizing theslow-to-operate ringing control relay R310. In the case underconsideration wherein the called line is an odd-numbered line, thecircuit for energizing this relay extends from the negative terminal ofthe exchange battery through the winding of the cut-oil? relay embodiedin the line circuit individual to the called line and by way of thecontacts 405, the conductor 460e, the contacts 803, C334, the contacts396, C336, the contacts 442, C329, the contacts 366, the winding 01'R310, and the contacts 322 to the grounded positive terminal of theexchange battery. It will be noted that this operating circuit for theringing control relay R310, as completed through the cut-off relayassociated with any oddnumbered line, includes the conductor C334. On

the other hand, ii an even-numbered called line is selected, theoperatin circuit for the ringing control relay R310 is slightlydifferent in that it extends from the conductor C336 by way of thecontacts 391, C335, and the operated private contacts of the countingrelays which correspond to the called lines. Thus, in the case of anoddnumbered called line, the ringing control relay R310 is energizedover an operating circuit including the contacts 396 and the conductorC334, and in the case of an even-numbered called line, this relay isenergized over a circuit including the contacts 391 and the conductorC335.

When energized over the above-traced circuit, the relay R310 operatesafter an interval to complete, at its contacts 31|, an obvious circuitfor energizing the relay R380. The relay R380 now operates and locks tothe grounded release conductor'C301 through its X contacts 385. At itscontacts 383, the relay R380 completes an obvious path forshort-circuiting the winding of the relay R310, thereby to render thelatter relay slow-torelease and to complete a path for impressing groundpotential directly upon the private conductor of the called line 0|,which path includes the conductors and contacts of the above-tracedoperating circuit for the relay R310. When this path is completed, thecut-off relay embodied in theline circuit individual to this line,operates to clear the line of the impedance represented by the windingsof the associated line relay. The application of ground potential to theprivate conductor of the called line 0| also guards this line againstseizure by any of the other connector

